Polyphonic percussion control apparatus



Feb. 21, 1961 J. M. HANERT 2,972,273

POLYPHONIC PERCUSSION CONTROL APPARATUS Filed March 12, 1958 2Sheets-Sheet 1 INVENTOR.

' Z7W a Feb. 21, 1961 J. M. HANERT 2,972,273

POLYPHONIC PERCUSSION CONTROL APPARATUS Filed March 12, 1958 2Sheets-Sheet 2 u E E!) 5 I D t 2 [II A 2 m 90 a I I I T I I 85 I I I I II I l I 0 l 2 3 4 5 c, 7 a 9 IO NUMBER OF KEYS PRESSED IN CUMULATIVESEQUENCE.

m I f r H J J 90 I j N Z I f u: so J U) I l 70 2 E L 3 5 0 I I I a 1 0-:a 5 4 5 c, 7 a 9 lo NUMBER OF KEYS SIMULTANEOUSLY PEESSED.

Jly 6 INVEN TOR.

50% M Jfiammi BY POLYPHONIC PERCUSSION CONTROL APPARATUS John M. Hanert,Des Plaines, Ill., assignor to Hammond Organ Company, Chicago, 111., acorporation of Delaware Filed Mar. 12, 1958, Ser. No. 720,887

18 Claims- (Cl. 841.26)

The invention relates generally to polyphonic percussion controlapparatus for incorporation in electrical musical instruments of thepolyphonic type. More particularly, the invention relates toimprovements in circuitry, whereby a percussion intensity envelope of atone will be produced upon the depression of a playing key, irrespectiveof whether other keys are being held depressed at the time.

In earlier conceived inventions for controlling the sounding of a tonewith a percussion intensity envelope, such as disclosed in applicantsprior application Serial No. 203,070 now abandoned, filed December 28,1950, of which this application is a continuation in part, some of theforms of the invention therein disclosed required that, in order toproduce-the tones with percussion intensity envelopes, the keys had tobe played in a staccato, or detached manner, and in others thepercussion intensity envelope was produced not only upon depression of akey while other keys were depressed, but also upon release of thehighest of a plurality of keys which had been depressed. Bothmodifications had some disadvantages as well as advantages, dependingupon the manner in which it was intended to control the sounding oftones with a percussion intensity envelope.

The present invention constitutes an improvement upon the form ofinvention disclosed in said application wherein the tone intensitypercussion envelope is produced upon depression of a key even though oneor more other keys are in depressed position.

It is therefore the primary object of the present invention to providepercussion intensity envelope control means, for an electrical musicalinstrument, in which the percussion envelope is produced upon depressionof any key despite the fact that other keys are being held depressed atthe time.

A further object is to provide a percussion tone intensity envelopecontrol means which is responsive to effect the production of apercussion tone even though a number of other keys have been depressedand are held in depressed position, and even though a number of keys aresimultaneously depressed. In the latter instance a percussion chord maybe sounded accurately to simulate chimes, bells, marimbas, guitar tones,and the like.

Other objects of the invention will appear from the followingdescription, reference being had to the accompanying drawing in which:

Fig. 1 is a schematic circuit diagram of one of the preferred forms ofthe invention.

Fig. 2 is a schematic circuit diagram which shows a desirable variationin circuitry for obtaining the producton of tones with percussiveintensity envelopes.

Fig. 3, is an elevation of a keyboard (partly in section), andassociated mechanism disclosing a further modification of the invention.

Fig. 4 is a vertical sectional view taken on line 44 of Fig. 3.

Fig. 5 is a graph indicating the amplitudes of the voltages produced,for the energization of the percussive envelope control circuitry, uponoperation of a number of keys played in cumulative sequence, and

Fig. '6 is a similar graph of the energizing voltages impressed upon thepercussive envelope control circuitry when a number of keys aredepressed simultaneously.

In general, there are two somewhat different aims to be accomplished incontrolling the production of tones with percussive intensity envelopes,depending upon whether the instrument in which such circuitry isemployed, namely, whether the instrument is of the monophonic typecapable of producing but one signal at a time or whether the instrumentis of the polyphonic type capable of producing simultaneously a numberof tone signals, i.e. chords.

The present invention is particularly adapted for use in instruments ofthe latter type, namely, polyphonic electrical musical instruments.

Referring to Fig. 1 the electrical musical instrument is illustrated ascomprising a plurality of electrical tone signal generators 10 which maygenerate tone signals of simple sine wave form but, preferably, ofcomplex wave form. A plurality of playing keys 12 are effective upondepression to close switches 14 to complete circuits through decouplingresistors R16 from the generators 10 to a signal collecting conductor18, and hence to the primary L20 of an output transformer T22. Thesecondary L24, of this transformer has its end terminals connected tothe control grids of triodes 2'6 and 27.

It will be noted that the other terminal of the input winding L20 isgrounded and that the other terminals of the tone signal generators 10are likewise grounded so that closure of any of the switches 14 willresult in impressing a tone signal on the primary winding L20. Theanodes of triodes 26 and 27 are connected to the terminals of theprimary L28 or an output transformer T30. A center tap of the primaryL28 is connected to a B+ terminal of the power supply while the cathodesof these triodes are connected to a +37 v. terminal power supply. Thesecondary L32 of the transformer T30 is coupled through an amplifier 34to a speaker 36.

As so far described, depression of any key 12 would result intransmission through the control triodes 26 and '27, transformer T30 andamplifier 34 to the speaker 36. However, the grids of control triodes 26and 27 are connected by a conductor 38, resistor R40, potentiometer R42,and resistor R44 to ground thus effectively biasing these triodes tocutoff by virtue of the fact that the cathodes of these triodes aremaintained at a +37 v. potential. A capacitor C46, connected between theconductor 38 and ground, is effective to limit the rate of attack byfiltering the high frequency transients.

The control of the intensity envelope control triodes 26 and '27 iseffected by the operation of switches" 48, respectively closed bydepression of the keys 12, to apply a negative pulse to a conductor 50.The switches 48 complete circuits between the conductor '50 and groundthrough parallel resistors R52 and R53, the resistor R53 havingcapacitor C54 in series therewith.

The value of the resistor R52 is preferably approximately ten times asgreat as that of the resistor R53. For example, resistors R52 and R53may have values in the order of 10 megohms and l megohm, respective,while the capacitor C54 may have a value of .001 mfd. The conductor 50is connected to a 8+ terminal of the power supply through a resistor R56which may have a value of approximately .1 megohm.

It will be pointed out hereinafter that irrespective of of whether oneor several of the keys '12 are depressed (despite the fact that severalother keys are held depressed at the time) will produce a negative pulseupon the conductor 50. This pulse is transmitted through capacitor C60and current limiting resistor R62 to the grid Patented Feb. 21, 1961 ofa triode 64. A grid return resistor R66 is connected between thejunction of capacitor C60 and resistor R62 and ground.

' The cathode of triode 64 is connected to ground through a self-biasresistor R68 having a bypass capacitor C70 in parallel therewith.Another current is supplied from a 'B+ terminal of the power supplythrough a load resistor R72. The output signal of triode 64 istransmitted from its anode through a capacitor C74 and current limitingresistor R76 to the control grid ofan amplifying and recti- -fyingtriode 78. The junction of capacitor C74 and resistor R76 is connectedto ground through a grid return resistor R80. The anode of triode 78 isconnected to'a +37 v. of the power supply, and its cathode is connectedto ground by means of conductor 82 and a capacitor C84, as well asthrough series connected resistors R42 and R44.

The operation of the circuitry shown in Fig. 1 may be well understood byreference to Figs. 5 and 6. When any one of the keys 12 is depressed it,of course, closes a switch 14 to supply the tone signal from itsgenerator to the primary L20 of transformer T22. At the same tor israpidly discharged and the potential on conductor 50 rather rapidlyrises to a value of approximately 99 volts due to current flow throughthe relatively high value resistor R52. Thus, a negative pulse istransmitted through capacitor C60 and resistor R62 and impressed uponthe control grid of triode 64.

Due to this pulse the triode 64 becomes non-conducting and the voltageon its anode increases to provide a pulse transmitted through capacitorC64 and resistor R76 to the control grid of triode 78, rendering thelatter temporarily conductive and causing a substantial increase in thepotential on its cathode and hence upon conductor 82, which increase inpotential is conducted through resistor R40 and conductor 38 to a centertap on the secondary L24 of transformer T22. This positive pulse also iseffective to charge capacitor C46 which also acts as a filter to removehigh frequency transients which might otherwise be applied to thecontrol grids of triodes 26 and 27. As

a result the potential on these triodes will rise at a rate determinedmainly by the time constant of capacitor C46 and resistors R40 (althoughthe capacitor C84 also has some effect) and, as a result, the triodes 26and 27 are substantially instantaneously rendered conductive of the'signal impressed upon the secondary L24 of the transformer T22. Thementioned components have a very short time constant, so that forpractical purposes, the pulse may be considered as instantaneouslyapplied to the grids of the triodes 26 and 27, although the fact thathigh frequency transients are filtered by virtue of the presence of thecapacitor C46, and that this capacitor is being charged at the time,prevents the potential on the control grids from rising so rapidly thatundesired audio frequency transients are not produced.

It will be apparent from the graph of Fig. 5 that as a .number of keysare depressed (and held depressed) in cumulative sequence the potentialon conductor 50 will be progressively reduced because of the successivedischarge of their associated capacitors CS4 to produce a sharp negativepulse adequately sufiicient to be transmitted through the triode 64, 78and their associated components to produce a rapid increase in thepotential on the control grids 26 and 27. As is apparent from Fig. 5,the potential on the conductor 50 drops rapidly and then rises more orless gradually to a value determined by the relative values of resistorsR16 and R56 operating as a voltage divider.

.A though the potential upon the conductor-50 as a result of successivedepression of a number of playing keys is progressively decreased, thenegative pulses, as above mentioned, are sufficiently great to insurereliable operation of the pulse controlled circuitry.

Referring to Fig. 6 which indicates the drop in potential upon conductor50 whena number of keys are simultaneously depressed, it will be clearthat upon the simultaneous depression of any number of keys, from 1 to10, a decided negative pulse will be impressed upon the conductor 50 'sothat the percussion envelope control circuitry will be operated in areliable manner.

It will be noted after the single key or any number of keys up to atleast 10 are depressed, the potential on the conductor 50 drops to acertain value, less than v., and then rapidly rises to the normalpotential of l-l-lOO v. I

From the foregoing, it will appear that a potential will be applied tothe control grids of triodes 26 and 27 every time one or a number ofkeys are depressed and that this voltage will be retained on these gridsas long as the capacitor C46 remains charged to a potential above thecutoff bias value, and that the discharge of the condenser will thuscause gradual decay of the output signal of the instrument. Thecapacitor C46 is discharged through resistors R40, R42, and R44, and therate of such discharge may be varied by adjustment of the potentiometerR42.

A modified form of the invention is shown in Fig. 2 wherein it isillustrated as producing the percussion effect either by solenoidoperated hammer of another type mechanical musical instrument or byproviding, as in the previous embodiment, for the application of a pulseto the control grids of a pair of push pull output control tubes.

In this modification each of the keys 12, upon depression,

closes two switches 94 and 96 preferably in the order named. Switch 94is effective to connect a musical tone signal generator 96 to a matchingtransformer 98 through a decoupling resistor R100. The signal is thustransmitted to the control grids of triodes 102 and 103. The center tapof the secondary of transformer 98 is connected to a termlnal -'50 v.through a resistor R104 so that these triodes are normally biased beyondcutoff because their cathodes are connected to ground through a commonself-bias resistor R106. The center tap of the transformer secondarywinding is also connected to ground through a capacitor C108 whichcorresponds generally to the capacitor C46 in the previously describedembodiment shown in Fig. l. The plates of triodes 102 and 103 areconnected in push pull to the primary of an output transformer 110, thecenter tap of which is connected to a B+ source of voltage. Thesecondary Winding of transformer 98 is coupled to a speaker 111 throughan additional amplifier 112 provided with the usual tone and expressioncontrols.

Each of the switches 96 has one pole connected to a conductor 114 whichis connected to a B+ terminal of the power supply while the otherterminal of each of these switches is connected through a resistor R116to a conductor 118. The conductor 118 is connected to ground through aresistor R120 which is of high value relative to that of each of theresistors R116. Conductor 118 is connected to the grid of a trioderectifier 122 through a blocking capacitor C124. The triode rectifier122 is normally biased beyond cutoff by connection to a 30 v. terminalthrough a grid resistor R126. Plate current for the triode 122 may besupplied either through a relay coil 128 upon closure of a switch 130 ormay be supplied through the winding of a solenoid 132 upon closure of aswitch 140, the switches 130 and each having one pole connected to a B+terminal. One contact of the switch 142, which is part of the relay 128,is connected to ground while the other pole thereof is connected to thecenter tap of the secondary of transformer 98.

With switch 130 closed, when any of the keys is depressed the closure ofits associated switch 94 results in impressing a tone signal across theprimary of transformer 98. In addition, a positive pulse is transmittedthrough capacitor C124. The time constant of the mesh comprisingcapacitor C124 and resistor R126 is very short so that the triode 122conducts but momentarily and the relay switch 142 is likewise closedbriefly, placing the grids of the control triodes 102, 103 at groundpotential. Thus the triodes 102, 103 are rendered conductive of thesignal at high amplitude to produce a percussive attack. The charge oncapacitor C108 is removed and therefore the triodes 102, 103 willcontinue to conduct the signal at decreasing amplitude as the capacitorC108 is recharged from the negative bias terminal 50 v. throughresistor-R104. Therefore, the operation of any one of the keys,irrespective of whether other keys are depressed at that time, willcause the tone to sound with a percussive envelope.

If desired, a switch 147 may be provided which, when closed, maintainsthe grids of the triodes 102 and 103 at ground potential. Under theseconditions the tones will sound in a customary sustained manner at asustained intensity determined by the usual volume control. Also,whenever desired, the switch 140 may be closed to cause operation of thesolenoid 132, the plunger of which may be connected to the hammer of anypercussive instrument,

such as the musical steel triangle 150, which is suitably suspendedabove a hammer 152 connected to be operated by the plunger of thesolenoid 132.

The time constant of C124 and R126 is made very short inorder to resolvethe pulses due to opening one of the contacts 96 and closing of anotherof these contacts when playing from one key to another in a legatomanner. Theoretically, the positive and negative pulses generatedthereby might cancel each other to produce no transient if the closingand opening of these switches occurred at exactly the same instant. Bythe use of a very short time constant, and also due to the momentaryunavoidable wiping effects of the contacts, a usable pulse is obtainedwith reasonable reliability.

It is to be noted that whenever a playing key is released, a negativepulse will be generated, but this pulse will have no effect upon triode122 because its grid is already maintained at a plate current cutoffpotential. Thus the percussive effect is obtained only by the depression(and not the release) of a playing key. This effect,

however, will be obtained even though other keys are being helddepressed. Thus the musician may obtain a series of percussive toneseven though he employs a legato playing technique.

In playing the instrument of the kind shown in Fig. 2 the musician hasmeans available for producing a variety of musical effects by operatingthe switches 130, 140, and 147 in various combinations. For example,assuming those of these three switches not mentioned as closed, areopen, the following effects may be obtained:

(1) With switch 147 closed the instrument played will perform in themanner of a customary organ;

,(2) With switches 140 and 147 closed the instrument will produce thecustomary organ tones accompanied by the percussion mechanicalinstrument tone of the steel triangle or the like;

(3) With switches 130 and 147 closed, the instrument will perform as ina customary organ because the center tap on the secondary transformerbeing already connected to ground by the switch 147 closure of the relayswitch 142 will not change the performance;

(4) With all three switches closed the instrument will perform as in (2)above, the customary organ tones and the mechnical percussion tones willbe produced;

(5) If all three switches are open no sound will be produced uponplaying the keys because the control tubes 102, 103 are biased beyondcutoff by their connection to the -50 v. terminal of the power supply;

(6) If only switch 140 is closed only the mechanical percussion tonefrom the steel triangle 150 will be sounded;

(7) If only the switch is closed, the tone produced will be a percussiontone of organ quality;

(8) If the switches 130 and are closed, the organ percussion tone willbe sounded together with the percussion tone from the steel triangle.

The musician thus has available the ability to employ these variouseffects in the rendition of a selection so as to add variety andinterest to the music.

The object of the invention may also be accomplished by the apparatusdisclosed in Figs. 3 and 4. In these figures the keys are'resilientlymounted on supports 162 and provided with sound deadening upstops 164and downstops 166 carried in a suitable keyboard frame channel 168. Eachof the keys has a hammer 170 resiliently secured thereto so arrangedthat when the key is depressed the hammer will engage a plate or bar-172associated with a microphone or vibration pickup 174, of anelectromagnetic or electrostatic type, which is powered by a battery 176and the output of which is supplied to an amplifier 178. This amplifiercorresponds to either the triode 64 of the embodiment shown in Fig. l orthe triode 122 of the embodiment of Fig. 2 and may be coupled to theoutput of the instrument in either of the manners shown in Fig. 1 orFig. 2.

It will be understood that the keys 160, in addition to energizing themicrophone 174, close switches such asthe switches 14 in Fig. 1 tocouple the signal generator to the matching transformer such astransformer T22 of Fig. 1 and 98 of Fig. 2.

As a key is depressed it first closes the switch to con nect the signalto the matching transformer and thereafter its hammer strikes the plate172 to energize the microphone or vibration pickup 174 and thus providethe pulse required for initiating the operation of the percussionintensity envelope control means, in the same manner as described abovewith reference to Figs. 1 and 2.

It will be readily apparent to those skilled in the art that, in some ofthe following claims, reference to negative peak voltage is not limitedto the provision of an intensity envelope control circuit in which anegative pulse is required, but that by simple changes of the circuitry,the latter may respond to a positive peak voltage, as for instance, byapplying a controlling voltage to the cathodes of the control tubes 26and 27 instead of to the grids of these triodes, or by interposing aphase or polarity reversing tube.

While I have shown and described particular embodiments of my invention,it will be apparent to those skilled in the art that numerousmodifications and variations may be made in the form and constructionthereof, without departing from the more fundamental principles of theinvention. I therefore desire, by the following claims, to includewithin the scope of my invention all such similar and modified forms ofthe apparatus disclosed, by which substantially the results of theinvention may be obtained by substantially the same or equivalent means.

I claim:

1. An electrical musical instrument of the polyphonic type capable ofproducing percussion tone effects, comprising a plurality of electricalmusical tone signal generators, a manual comprising a plurality ofplaying keys, an output system including electrical pulse sensitiveunitary means for producing tones having a percussion type intensityenvelope, means operable by the playing keys respectively to couple thegenerators to the output system, a conductor coupled to the input ofsaid unitary means, a source of electrical energy, an electricalimpedance coupling said conductor to one terminal of the source, aplurality of individual impedance means associated respectively with thekeys, each of said individual impedance means having one terminalcoupled to the other .prising a plurality of erators; a manual terminalof the Source, and switches respectively operable by.the keys to couplethe other terminals of said impedance means to, said conductor, wherebyupon depression 4. The'combination set forth in claim 1 in which,

upon operation of the playing keys, the impedance means connected in thecircuit by the operation of the playing keys, cause a changed voltagedivision resulting in producing pulses when the keys are operated incumulative sequence.

' 5. The combination set forth in claim 1 in which the pulses producedon the conductor by the cumulative depression of a number of keys havesuccessively lower peak voltage values, and in which the pulse producedupon depression of another key while holding a plurality of other keysdepressed is of sufficient peak voltage ,to cause reliable operation ofthe unitary percussive intensity envelope tone producing means.

'6. The combination set forth in claim 1 in whichthe impedance meanswhich are connected in the circuit by the playing keys compriseindividual resistors.

7. The combination set forth in claim 1 in which the means for producingthe electrical pulses comprises a microphonic element, and in which eachof the keys is provided with means to produce a mechanical shock to themicrophonic element thereby to cause the latter to generate a pulse.

8. The combination set forthin claim 1 in which the unitary percussionintensity envelope producing means includes an electromagneticallyoperated percussion sound producing instrumentality.

9. The combination set forth in claim 1 in which said unitary percussionintensity envelope producing means includes a rectifier having input andoutput circuits, and in which the output circuit of the rectifying.means includes means for supplying a potential to a terminal of saidunitary means initially of such value to cause the signal suppliedthereto to be conducted through the output system at maximum amplitude,and includes a resistance capacitance. circuit for gradually reducing,the potential on said terminal of the tone intensity envelope producingportion of the output system, to cause gradual decay in the intensity ofthe tone produced.

10. An electrical musical instrument of the polyphonic type capable ofproducing percussion tone elfects, comelectrical musical tone signalgencomprising a plurality of playing keys; an output system includingunitary means for producing tones having a percussion type intensityenvelope; means operable by the playing keys respectively to couple thegenerators to the output system; rectifying means; circuit means,coupling the output of the rectifying means to the percussion intensityenvelope controlling means to energize the latter upon transmission ofan electrical pulse through said rectifying means; a conductor coupledto the input of said rectifying means; a sourceof electrical energyhaving one terminal connected to said conjduct'or; an impedance elementincluded in said connection between said terminal and said conductor;impedancemeans respectively associated with each of the keys,

and means respectively operated by the keys to connect said impedancemeans between said conductor and the other terminal of said energysource, whereby upon depression of a key .an electrical pulse will beimpressed on said conductor irrespective of whether other keys are ina'depressed position.

11. In an electrical musical instrument, having tone signal generators,and means for producing percussive type tones, the combination of amanual comprising a plurality of keys, an output system including toneintensity envelope control means having a terminal the potential ofwhich is determinative of the amplitude of the tone signals transmittedthrough the output system, means respectively operable by the playingkeys to couple the tone signal generators to the output system, aplurality of impedance means, a source of potential, means operable bythe keys respectively to connect the impedance means between theterminals of the source of potential thereby to produce pulses,electromagnetic means, means responsive to the pulses to provide currentfor the energization of at least one of the electromagnetic means, meansresponsive to the energization of one of the electromagnetic means toapply a potential to said terminal of the tone intensity envelopecontrol means to cause transmission of the tone signal supplied theretoby the generators through the output system at high amplitude, decaycircuitry means coupled to said terminal for causing a gradual change inthe potential on said terminal to a value such that the tone signals arenot transmitted through the output system, means operable by another ofsaid electromagnetic means to actuate a mechanical musical soundproducer, and switch means manually operable to render either or both ofsaid electromagnetic means effective.

12. In an electrical musical instrument, means for producing percussivetype tones, the combination of a plurality of generators of electricmusical tone signals,

a manual comprising a plurality of keys, an output system including toneintensity envelope control means having a terminal the potential ofwhich is determinative of the amplitude of the tone signals transmittedthrough the output system, means respectively operable by the playingkeys to couple the tone signal generators to the output system, aplurality of impedance means, a source of potential, means operable bythe keys respectively to connect the impedance means between theterminals of the source of potential thereby to produce pulses,electromagnetic means, means responsive to the pulses to provide currentfor the energization of the electromagnetic means, means responsive tothe energization of the electromagnetic means to apply a potential tosaid terminal of the tone intensity envelope control means of value suchas to cause transmission of the tone signals through the output systemat high amplitude, decay circuitry means coupled to said terminal forcausing a gradual change in the potential on said terminal to a valuesuch that the tone signals are not transmitted through the outputsystem.

13. In an electrical musical instrument of the polyphonic type havingmeans for producing a percussion efiect upon depression of a keyirrespective of whether other keys are depressed at the time, thecombination of a plurality of electrical musical tone signal generators,a manual comprising a plurality of playing keys, an output systemincluding tone intensity envelope control means, the latter having aterminal the potential of which determines the amplitude of a signaltransmitted through the output system, means operated by the keys tocouple the generators respectively to the output system,

- amplitude, switches respectively operated by the playing .keys toproduce an electrical pulse and thereafter to maintain a supply ofconstant voltage, a conductor common to the switches of all of the keysto receive the pulses and to have the potential thereon maintained uponclosure of one of the key operated switches, electronic means responsiveto the application of a pulse to said conductor effectively to couplethe potential source to said terminal of the tone intensity controlmeans, a

v ductor;

fixed voltage of such value that when applied to said terminal preventstransmission of the signal, and resistance means connected between saidterminal and said fixed voltage source operable gradually to change thepotential on said terminal to a value which renders said tone intensitycontrol means ineffective to transmit the tone signals supplied thereto.

14. An electrical musical instrument of the polyphonic type capable ofproducing percussion tone effects, comprising a plurality of electricalmusical tone signal generators; a manual comprising a plurality ofplaying keys; an output system including unitary means for producingtones having a percussion type intensity envelope; means operable by theplaying keys respectively to couple the generators to the output system;rectifying means; circuit means coupling the output of the rectifyingmeans to the percussion intensity envelope controlling means to energizethe latter upon transmission of an electrical pulse through saidrectifying means; a conductor coupled to the input of said rectifyingmeans; a source of electrical energy having one terminal connected tosaid conductor; a plurality of impedance means respectively associatedwith the keys; and means respectively operated by the keys to connectsaid impedance means between said conductor and the other terminal ofsaid energy source, whereby upon depression of a key an electrical pulsewill be impressed on said conductor irrespective of Whether other keysare in a depressed position.

15. An electrical musical instrument of the polyphonic type capable ofproducing percussion tone effects, comprising a plurality of electricalmusical tone signal generators; a manual comprising a plurality ofplaying keys; an output system including unitary means for producingtones having a percussion type intensity envelope; means operable by theplaying keys respectively to couple the generators to the output system;rectifying means; circuit means coupling the output of the rectifyingmeans to the percussion intensity envelope controlling means to energizethe latter upon transmission of an electrical pulse through saidrectifying means; a conductor coupled to the input of said rectifyingmeans; a source of electrical energy having one terminal coupled to saidconan impedance included in said coupling between said terminal and saidconductor; impedance means respectively associated with each of thekeys; and means respectively operated by the keys to couple saidimpedance means between said conductor and the other terminal of saidpotential source, whereby upon depression of a key an electrical pulsewill be impressed on said conductor irrespective of whether other keysare in a depressed position.

16. In an electrical musical instrument of the polyphonic type forproducing percussion tone effects, the combination of a plurality ofelectrical musical tone signal generators, an output system comprisingan amplifier and speaker, said amplifier having a terminal the potentialof which determines the degree of amplification thereof, a plurality ofkeys, means respectively operated by the keys to cause the generators totransmit tone signals to the output system, a conductor, a rectifierhaving its input coupled to said conductor, means coupling the output ofthe rectifier to said terminal of the amplifier, a source of electricalenergy, an electrical impedance connecting said conductor to oneterminal of the source, a plurality of individual elements associatedrespectively with the keys, each impedance element having one terminalconnected to the other terminal of the source, and switches respectivelyoperable by the keys to connect the other terminals of said impedanceelements to said conductor.

17. In an electrical musical instrument of the polyphonic type forproducing percussion tone effects, the combination of a plurality ofelectrical musical tone signal generators, an output system comprisingan amplifier and speaker, said amplifier having a terminal the potentialof which determines the extent of amplification thereof, a plurality ofkeys, means respectively operated by the keys to cause the generators totransmit tone signals to the output system, a conductor, means couplingthe conductor to said amplifier terminal, a source of electrical energy,an electrical impedance connecting said conductor to one terminal of thesource, a plurality of individual impedance elements associatedrespectively with the keys, each impedance element having one terminalconnected to the other terminal of the source, and switches respectivelyoperable by the keys to connect the other terminals of said impedanceelements to said conductor.

18. In an electrical musical instrument of the polyphonic type forproducing percussion tone effects, the combination of a plurality ofelectrical musical tone signal generators, an output system comprisingan amplifier and speaker, said amplifier having a terminal the potentialof which determines the extent of amplification thereof, a plurality ofkeys, means respectively operated by the keys to cause transmission oftone signals from the generators to the output system, a conductor,means coupling the conductor to said terminal, a source of electricalenergy, an electrical impedance connected between said conductor and oneterminal of the source, a plurality of individual impedance elementsassociated respectively with each of the keys and having one terminalconnected to the other terminal of the source, and switches respectivelyoperable by the keys to connect the other terminals of said impedanceelements to said conductor.

References Cited in the file of this patent UNITED STATES PATENTS2,486,208 Rienstra Oct. 25, 1949

